We propose to study the biochemistry of infective forms of Trypanosoma rhodesiense bloodstream trypomastigotes maintained in vitro at 37 degrees C on Chinese hamster lung tissue culture cells. The primary objectives of this research project are to: 1. Develop procedures for the maintenance on easily derived tissue culture cells of T. rhodesiense trypomastigotes infective for laboratory animals. 2. Determine whether the biochemical properties of T. rhodesiense cultured infective trypomastigotes are similar to bloodstream trypomastigotes or procylic trypomastigotes. 3. Compare the antigenic properties of T. rhodesiense cultured infective trypomastigotes with bloodstream trypomastigotes and procyclic trypomastigotes. 4. Determine whether a switch of the surface antigen on T. rhodesiense cultured infective trypomastigotes can occur in vitro. Our major goal is to be able to develop an in vitro system for the cultivation of T. rhodesiense which will be useful in studying antigenic various.